1. Field of the Invention
This invention relates to a magnetic recording device suitable for use with video tape recorders. More specifically, to an azimuth recording method magnetic recording/reproducing device incorporating a 2-channel and a 4-channel recording mode in one device in which a pair of magnetic recording heads for a first head width, and a pair of magnetic recording heads for a second head width narrower than the first head width are installed along a common imaginary line along the direction of head drum rotation, and information recorded by means of the magnetic head pair for the second head width is overlapped on both sides of the boundary lines of the magnetic recording zone of the tape recording medium already recorded upon by the magnetic head pair for the first head width.
2. Description of Related Art
In recent years, many video tape recorders utilize an azimuth recording system for high density recording of audio and video signals. In video tape recorders using this method, a pair of recording heads having an azimuth angle are installed on the head drum, and the head drum rotates so that the recording head diagonally scans the tape record medium (hereafter referred to as "tape"). Information is first recorded on the tape recording surface by means of the lead recording head and after this recording, information is continuously recorded by means of a lag recording head which follows up the action of the lead recording head.
The structure of a magnetic recording/reproducing device of the conventional art using the azimuth recording system is shown in FIG. 12. A pair of magnetic recording heads (hereafter called "recording heads") 2A and 2B are installed in mutual proximity along the rotation direction of the drum. The recording head 2A is the lead (or prior) head and the recording head 2B is the lag (or follow-up) head. A tape 7 is scanned while wound 180 degrees around the drum as shown in the figure.
A pair of magnetic heads for reproduction (hereafter called "reproduction heads") 2C and 2D are installed in a position 180 degrees deviated from the recording heads 2A and 2B on the head drum 1 as shown in FIG. 13.
On the head gap surface of this pair of recording heads 2A and 2B, the upper edge of the lead recording head 2A and the lower edge of the lag recording head 2B are arranged on the common line La as shown in FIG. 14. In other words, comprising a high density recording method without a guard band.
When the azimuth angle of the recording head 2A is +.theta., the azimuth angle of the other recording head 2B is selected at -.theta.. The head width Hw of the recording head 2A is the track width Tw. The head width Hw of the recording head 2B is the track width Tw as shown in FIG. 15.
However, when required that a large amount of information be capable of being recorded on the tape 7, if recording is performed without a guard band while the height difference h which is a difference between the upper edge of the recording head 2A and the upper edge of the recording head 2B as shown in FIG. 14 is reduced, then a large amount of information can be recorded compared to when the height difference h is equal to the head width Hw of the recording head 2B. For instance, when the recording head 2B is placed so that the head difference h is one half of the head width Hw, then when the tape drive speed is set to 2.multidot.Tw, twice the amount of recording information can then be recorded on the same length of tape.
However, in the magnetic recording/reproducing device of the conventional art, this height difference h is fixed at the time when the recording heads 2A and 2B are installed on the head drum 1. This height difference h as is, becomes the track width (=track pitch Tp ) Tw as shown in FIG. 15.
Consequently, even if able to reduce the height difference h and perform high density recording, setting the track width Tw to half the size and performing 4-channel recording makes it impossible to record information at double the density on the tape 7 or return the track width to the former width and make recordings for a 2-channel recording mode device.
Consequently, the problem exists that when tape editing for 2-channel record mode devices and tape editing for 4-channel record mode devices is required, 2-channel recording mode and a 4-channel recording mode cannot both be performed in one magnetic recording/reproducing device.